Pneumococcus is a bacterium that healthy people commonly have in their nose and throat;this is called pneumococcal 'carriage'. Carriage is usually harmless, but can progress to serious disease like pneumonia, meningitis, and blood stream infections or to less serious, but burdensome, diseases like sinusitis or ear infections. Infants and the elderly bear the greatest burden of pneumococcal disease with over 800,000 annual global deaths from this germ among children under 5 years of age. Furthermore, pneumococcus has developed resistance to antibiotics making it increasingly difficult to treat pneumococcal infections. Within the United States some Native American groups, like the Navajo and the White Mountain Apache tribes, suffer from pneumococcal disease much more often than people in the general US population. We don't know why pneumococcus disproportionately afflicts these communities, but we know this health disparity can be significantly reduced through vaccination. In 2000 for the first time a pneumococcal vaccine designed specifically for infants, called PCV7, became available and was put into routine use among Navajo, Apache as well as the general US population. PCV7 contains the 7 most common of the >90 pneumococcal strains that exist. Although PCV7 is only given to infants and toddlers, it impacts pneumococcal disease throughout the community because it not only protects vaccinated infants from disease it also protects them against NP colonization. Infants and children are the main transmitters of pneumococcal colonization in the community so any change in their carriage affects the whole population of pneumococcal germs circulating within the family and community. Reductions in pneumococcal disease caused by the 7 types in PCV7 have exceeded expectations, especially among Navajo and Apache where we have seen no cases in over 4 years. But, PCV7 has had the unintended consequence of increasing the amount of pneumococcal disease from some pneumococcal types that are not in PCV7. Therefore a new vaccine to protect against 13 pneumococcal strains, called PCV13, is about to be licensed and used. This project aims to reveal the impact of PCV13 on pneumococcal disease and carriage of strains which move from person to person within the Navajo and Apache communities. We specifically intend to find out if use of PCV13 has an effect on disease and carriage of the 6 additional strains in the vaccine and to find out if PCV13 will result in the emergence of new pneumococcal serotypes within the community, like PCV7 did. This information will allow us to design vaccine strategies to meet these new patterns of pneumococcal disease and stay at least one step ahead of the organism changes.